Right at full, slightly over. My line of thinking is 4 kids in a kiddie pool get if filthy pretty quick. Those same 4 kids wouldn't make a dent in an olympic sized pool. The larger the volume of fluid, the more than any input is spread out: fuel soot, heat, whatever. In some cars, the difference between min and max is a quart. In a 4 quart system, thats 25%...a major difference.
I have noticed, at least in my 2002 Ford Taurus with 148k miles, that their is more burn off towards the top of the "fill" mark. Then as it gets to the middle of the dip stick it slows and stops. I am beginning to think that the car really likes closer to 4.5 quarts, that last pint just gets burned over the first 3,000 miles of the OCI.
This is a series of experiments I have yet to do.
I keep mine of Max full. I like the reserve for long trips or when my wife is about to depart a a 4k mile road trip I just changed the oil and filled it to Max(knowing that she won't open the hood once in this cross country drive). When she comes home I will check the oil kevel and top it off to Max to finish up the OCI if it is needed.
I keep all my fluids to the max line as well.
Currently my engine oil is slightly over max, as I had a 4.4L jug and my car takes 4.3L, I dumped it all in, what would I do with 0.1L of oil? My car doesn't burn any oil (looking at oil level shown on the dipstick).
Like many of us, my cars don't burn oil enough to measure.
So the level stays at the top.
The only advantage to running lower oil leveles is less drag by the crank and rods . And this is only a possibility, not something we can count on every time.
To the "full" mark, or slightly over for my automatic transmission. It shifts better with the extra fluid in there.
Shifts better? Really? Going beyond “Max” is overfilling, and it can cause foaming and sluggish trans performance.
It doesn’t make sense to me, “Max” means exactly what it means, “Maximum”...i.e. the limit/ceiling, don’t go beyond.
You also have to consider the vehicle. The gas engine in the Prius, for example, is known to be sensitive to even slight overfilling, and many on the Prius boards feel that a few ticks below FULL is the optimum level. I've also heard that the GM Northstar V-8 is similarly sensitive (but I have no idea about the value of that info).
I think it's safe to say that for the vast majority of the motoring public, shooting for the full line is the safest approach. For certain groups, however, a different strategy may be warranted. When in doubt, learn more.
" shooting for the full line is the safest approach"
There are a few engines, or individual engines among an engine family that seem to seek a level about a 1/2 qt low.
Add to the full, it'll burn that half a qt. Leave it there and it won't burn anymore than that.
Odd, but it happens.